Scalable polarimetric phased array transceiver

ABSTRACT

A polarimetric transceiver front-end includes two receive paths configured to receive signals from an antenna, each receive path corresponding to a respective polarization. Each front-end includes a variable amplifier and a variable phase shifter; a first transmit path configured to send signals to the antenna, where the transmit path is connected to the variable phase shifter of one of the two receive paths and includes a variable amplifier; and a transmit/receive switch configured to select between the first transmit path and the two receive paths for signals, where the transmit/receive switch includes a quarter-wavelength transmission line that adds a high impedance to the transmit path when the transmit/receive switch is in a receiving state.

RELATED APPLICATION INFORMATION

This application claims priority to provisional application Ser. No.61/746,646 filed on Dec. 28, 2012, incorporated herein by reference.

GOVERNMENT RIGHTS

This invention was made with Government support under Contract No.HR0011-11-C-0136 awarded by Department of Defense (DOD). The Governmenthas certain rights in this invention.

BACKGROUND

1. Technical Field

The present invention relates to millimeter-wave transmitters andreceivers and, more particularly, to polarimetric phased arraymillimeter-wave transceivers.

2. Description of the Related Art

Millimeter-wave (mmWave) communications provide large bandwidth, shortwavelengths, and the ability to operate in dusty and foggy conditions.As a result, mmWave systems are attractive for high data ratecommunications and high-resolution imaging applications. These featurescan be further bolstered by the use of dual-polarization communications,which are advantageous in to imaging systems with degraded visibility.

Current integrated phased array systems do not support dual-polarizationcommunications, are not flexible enough to support multipleapplications, and are not scalable to large numbers of elements.Non-integrated solutions for using dual-polarization communication inmmWave systems are based on discrete electrical and mechanical modulesand add significant weight and size.

SUMMARY

A polarimetric transceiver front-end includes two receive pathsconfigured to receive signals from an antenna, each receive pathcorresponding to a respective polarization, each front-end including avariable amplifier and a variable phase shifter; a first transmit pathconfigured to send signals to the antenna, said transmit path beingconnected to the variable phase shifter of one of said two receive pathsand including a variable amplifier; and a transmit/receive switchconfigured to select between the first transmit path and the two receivepaths for signals, the transmit/receive switch including aquarter-wavelength transmission line that adds a high impedance to thetransmit path when the transmit/receive switch is in a receiving state.

A polarimetric phased array transceiver includes a plurality offront-ends configured to transmit and receive signals; a first powercombiner configured to combine the received signals from a first receivepath of each of the plurality of front ends; and a second power combinerconfigured to combine the received signals from a second receive path ofeach of the plurality of front ends and further configured to split atransmission signal to the transmit path of each of the plurality offront ends. Each front-end includes two receive paths configured toreceive signals from an antenna, each receive path corresponding to arespective polarization, each including a variable amplifier and avariable phase shifter; a first transmit path configured to send signalsto the antenna, said transmit path being connected to the variable phaseshifter of one of said two receive paths and including a variableamplifier; and a transmit/receive switch configured to select betweenthe first transmit path and the two receive paths for signals, thetransmit/receive switch including a quarter-wavelength transmission linethat adds a high impedance to the transmit path when thetransmit/receive switch is in a receiving state.

A polarimetric phased array transceiver includes a plurality offront-ends configured to transmit and receive signals associated with arespective dual-polarization antenna; a first power combiner configuredto combine the received signals from a first receive path of each of theplurality of front ends; a second power combiner configured to combinethe received signals from a second receive path of each of the pluralityof front ends and further configured to split a transmission signal tothe transmit path of each of the plurality of front ends; and a signaldistribution network configured to accept a local oscillator signalinput and to retransmit the local oscillator signal to one or more otherpolarimetric phased array transceivers and further configured to acceptcombined signals from the power combiners and to combine said combinedsignals with respective signals from one or more other polarimetricphased array transceivers. Each front-end includes two receive pathsconfigured to receive polarized signals from the antenna, each receivepath corresponding to a respective polarization, each including avariable amplifier and a variable phase shifter; a first transmit pathconfigured to send signals to the antenna, said transmit path beingconnected to the variable phase shifter of one of said two receive pathsand comprising a variable amplifier; and a transmit/receive switchconfigured to select between the first transmit path and the two receivepaths for signals, the transmit/receive switch including aquarter-wavelength transmission line that adds a high impedance to thetransmit path when the transmit/receive switch is in a receiving state.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 is a block diagram of a polarimetric phased array transceiver inaccordance with the present principles;

FIG. 2 is a block diagram of a polarimetric phased array front-end inaccordance with the present principles;

FIG. 3 is a schematic of a low-noise transmit/receive switch inaccordance with the present principles;

FIG. 4 is a block diagram of signal distribution between a set ofpolarimetric phased array transceivers in accordance with the presentprinciples;

FIG. 5 is a block diagram of received signal combination from a set ofpolarimetric phased array transceivers in accordance with the presentprinciples;

FIG. 6 is a block diagram of a digital control for polarimetric phasedarray front-ends in accordance with the present principles;

FIG. 7 is a block/flow diagram of a method of using a polarimetricphased array transceiver in accordance with the present principles;

FIG. 8 is a block diagram of an alternative embodiment for apolarimetric phased array front end in accordance with the presentprinciples; and

FIG. 9 is a schematic of a simplified low-noise transmit/receive switchin accordance with the present principles.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention provide millimeter-wave (mmWave)phased array transceivers, where each element in the array allows forsimultaneous reception in two polarizations. A transmitter portion ofthe transceiver is capable of transmitting on each polarization inalternation using a dual-polarized antenna. Thus each front-end has twoindependent receiving (RX) paths and a transmission (TX) path with twooutputs. A switch changes between RX and TX modes. Whereas a traditionalswitch would have a significant impact on performance, since theinsertion loss directly degrades the RX noise figure, the switchdescribed herein minimizes the impact on the noise figure.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, a general diagram of adual-polarization phased array transceiver 100 is shown. The transceiver100 includes multiple dual-polarization front ends 102, each having anassociated antenna 101 capable of transmitting and receiving on twodifferent polarizations. To accomplish this, the antenna 101 may includemultiple physical receiving/transmitting elements that are configured toreceive/transmit their respective polarizations. One specific design foran exemplary antenna 101 may be a dual-polarized patch antenna. For easeof description, the embodiments set forth herein will be described astransmitting on a horizontal (H) and a vertical (V) polarization, thoughit should be recognized that any suitable polarization, includingleft-handed and right-handed polarizations, can be used instead.

Each front end 102 includes two receive chains 104 and a transmit chain106. When the transceiver 100 receives signals, the antennas 101 producerespective received polarized signals that arrive at front end 102. Eachsignal passes through a respective H or V transmit/receive switch 108before arriving at receive chain 104. The receive chains 104 performsamplification and phase shifting of the received signal, as will bedescribed in greater detail below. In this manner, the front ends 102may perform beam steering to selectively receive signals arriving from aparticular direction.

The V receive chain 104 of each front end 102 provides its output to a Vpower combiner 110 that combines the signals from each of the variousfront ends 102 along the vertical polarization into a single receivedsignal. Similarly, the H receive chain 104 of each front end 102provides its output to the H power combiner/splitter, which combines allreceived H-polarized signals. The two power combiners 110 and 112 outputtheir respective combined signals to signal processor 114, whichtransforms the received signals into an appropriate encoding andfrequency for subsequent use.

During transmission, the signal paths are reversed. A transmissionsignal is provided by signal processor 114 to H power combiner/splitter112. In the present embodiments only one transmission signal isemployed. Those having ordinary skill in the art will recognize that thetransmission signal may be equivalently provided along the H or V signalpaths. In the present case, the H power combiner/splitter 112 receivesthe transmission signal and distributes it to each of the front ends102. Additionally, although the depicted embodiments show only a singletransmission chain 106, the present principles may also be applied toembodiments having two complete transmission chains that can transmitsimultaneously in respective polarizations.

The transmitted signal branches from the receive chain 104 to transmitchain 106, where it is amplified and sent to the antenna 101 by way ofone or both of the transmit/receive switches 108. It should berecognized that switches 108 may be configured to selectively transmitsignals along a single polarization or along both polarizations.

In one specific embodiment, the transceiver 100 may have 16radio-frequency phase shifting front ends 102. Alternatively, this maybe conceived of as 32 distinct receive chains 104, grouped into two setsof 16 elements—one for each antenna polarization.

Referring now to FIG. 2, a detailed view of a front ends 102 is shown.As noted above, the front end 102 has two receive paths 104 and onetransmit path 106. The receive paths amplify the received polarizedsignals with low-noise amplifiers 204 and variable amplifiers 206according to beam steering parameters. The receive paths then phaseshift the amplified signals at variable phase shifters 202 according tobeam steering parameters. The front end 102 may provide digital controlof the variable amplifiers 206 and the variable phase shifters 202according to locally stored parameters or based on signals received froman external control module. The phase shifters 202 may be passive,bi-directional, reflection-type phase shifters with an exemplary phaserange of 180 degrees. Sharing the phase shifters 202 between thetransmit and receive paths saves a substantial amount of area.

As described above, one of the receive paths 104 splits off intotransmit path 106. Two switches 208 govern whether the phase shifter 202is used to transmit or receive at a given time. Two additional switches208 at the output of the transmission path determine which polarizationis used to transmit a signal.

The transmission path 106 receives a signal from the variable phaseshifter 202 of one of the receive paths 104 by way of a switch 208. Thetransmission path includes a variable amplifier 210 and a 212 thatfunction similarly to those in the receive path. The amplified signal ispassed to an active power splitter 214 that generates two transmitsignals, one along each polarization. It should be noted that thevariable amplifiers may also serve the function of a phase inverter.Each path needs 360 degrees of beam steering range, so if phase shifter202 provides 180 degrees, another discrete step of 180 degrees isneeded. In the present embodiments, this discrete step may be providedby the variable amplifiers 206 and 210.

The phase shifter 202, the amplifiers 206 and 210, and the switches 208may be controlled digitally by the front end 102. Each operatingcharacteristic (e.g., transmission, reception, polarization, phaseshift, gain) is defined by a set of digital controls 218. As will bedescribed in greater detail below, a memory and logic unit may beincluded in the front end 102 to provide agile switching betweendifferent modes of operation. Pre-defined sets of control bits arestored and then applied to the circuitry as required by the overallsystem.

Referring now to FIG. 3, greater detail is provided on the region of thefront end 102 that connects the output of amplifier 214 in the transmitpath 106, the input to amplifier 204 in the receive paths 104, and theantenna 101. Switching is activated by transistor 314. When the switch314 is off, the linear amplifier input 316 (drawing power from a powersource 318 via a transmission line 307) is also turned off and thetransmit path input 302 is active. It should be noted that the transmitpath input 302 will be shared between two switches 208, allowing thetransmit path input 302 to be fed to either of the two outputpolarizations. A switch control 304 turns the transmission of input 302on and off, with a power source 308 connected via a transmission line307, allowing the transmission output polarization to be controlled. Inthe present embodiments, the transmit path input 302 receives one outputof active power splitter 214. In this configuration, the input from thetransmit path maximizes the power delivered to the antenna 101 at output322. A DC biasing input 302 is also provided.

In receiving mode, the switch 314 is on, presenting a low impedance toground on the transmit path 106. A quarter-wavelength transmission line306 transforms the short load of the switch 314 such that the transmitpath 106, as seen from the receive path 104 at the received wavelength,presents a high impedance. Input matching from the low noise amplifier204 in the receive path 104 is configured to attain the lowest possiblenoise factor when active and presents the highest impedance possiblewhen inactive. A bypass capacitor 320 has a low series impedance at thetarget receiving frequency.

In transmission mode, the switch 314 is off. Signals from the transmitpath input pass through a bypass capacitor 310 having a low seriesimpedance at the transmission frequency. The transmission signalsproceed to the antenna output 322 by a path common to the receiving path104.

Referring now to FIG. 4, signal distribution for a local oscillator (LO)signal is shown. To make phased array transceiver chips 400 suitable foruse in larger, scalable arrays, LO signals from different chips 400 needto be distributed or combined in a coherent fashion. Toward this end,on-chip buffers for a given transceiver chip distribute an incoming LOsignal 402 to two different outputs 404. The outputs may then, in turn,be connected to a next level in an array hierarchy of chips 400. Thechips 400 use the LO signal as a reference and may modify the LO signalaccording to the signal frequencies needed.

Referring now to FIG. 5, signal combination for an intermediatefrequency (IF) signal having a received signal is shown. A set oftransceiver chips 500 are connected linearly, with each chip 500 addingits received signal 502 from front ends 102 to an output 504 of theprevious chip(s) 500 to form a combined output 506. A similar structurefor signal distribution may be used for transmission signals. In thismanner, arbitrarily large numbers of chips may be connected to form alarge-scale array. It should be recognized that increasing the number ofchips will increase an amount of phase delay between each respectivechip. However, the phase shifter 202 at each front end 102 compensatesfor this phase delay when providing beam steering parameters.

Referring now to FIG. 6, a diagram of digital control 218 is shown.Steering the beam, or switching between transmission and reception,involves changing the digital signals being provided to the phaseshifter 202, the variable amplifiers 206 and 212, and to the switches216. In one exemplary embodiment, a 24-bit digital word controls all ofthe parameters of a given front end 102, with 16 such front-ends 102being on a single chip 100. Although it is possible to load thesecontrol words across all of the (potentially thousands of) chips, suchloading could take a substantial amount of time and slow theresponsiveness of the system.

To address this issue, all of the possible beam configurations andcorresponding parameters may be stored on-chip in a memory 602 ofdigital control 218. A central, off-chip control may then issue acommand to each of the chips 100 that includes only a pointer to alocation in a beam configuration register 606 stored in memory 602 thatcorresponds with the configuration for that chip 100. The digitalcontrol 218 receives this instruction and processor 604 finds theappropriate configuration parameters, applying them to the respectivedevices on the chip 100. In this exemplary embodiment, with 32 beamdirections stored in the register 606 and about two thousand differentregister entries, one megabyte of storage or more may be needed to storeall of the pertinent beam parameters.

Digital control of the chips 100 may be implemented in parallel, witheach chip 100 being sent a signal along an individual communicationline, in serial, with each chip's instructions being sent along a seriallink of chips 100, or in a hierarchically distributed fashion. Forexample, each chip 100 may receive instructions and distribute them to aset of other chips 100, farther down on the hierarchy. This repeatsuntil all chips 100 have received the appropriate beamforminginstructions.

Referring now to FIG. 7, a method for controlling a dual-polarizationphased array transceiver is provided. As noted above, control may beperformed at a central location or may be distributed. Block 702configures the phase shifters of each front-end according to beamsteering parameters. These parameters generally include a phase shiftfor each front end 102 in each chip 100 and provide a delay betweensuccessive signals, such that the gain of the array is enhanced in aparticular direction.

Block 704 selects a transmission or reception mode for the array. Asdescribed above, this selection involves the setting of switches 216 tocause signals to path through the reception paths 104 or thetransmission path 106. If the transmit mode is selected, block 706configures the transmission amplifier 210 according to the beam steeringparameters. Block 708 selects a polarization for transmission usingswitches 216. The present embodiments select only one polarization fortransmission, while allowing receipt of signals on both polarizations.Block 710 then transmits the signal from the front ends 102 using theappropriate beam steering. If receive mode is selected, block 712configures reception amplifiers 206 according to the beam steeringparameters. Block 714 then receives signals along both polarizations,using two distinct receive paths 104 to process the signals.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing. Computer program code for carrying out operations foraspects of the present invention may be written in any combination ofone or more programming languages, including an object orientedprogramming language such as Java, Smalltalk, C++ or the like andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The program codemay execute entirely on the user's computer, partly on the user'scomputer, as a stand-alone software package, partly on the user'scomputer and partly on a remote computer or entirely on the remotecomputer or server. In the latter scenario, the remote computer may beconnected to the user's computer through any type of network, includinga local area network (LAN) or a wide area network (WAN), or theconnection may be made to an external computer (for example, through theInternet using an Internet Service Provider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks. The computer program instructions may also beloaded onto a computer, other programmable data processing apparatus, orother devices to cause a series of operational steps to be performed onthe computer, other programmable apparatus or other devices to produce acomputer implemented process such that the instructions which execute onthe computer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblocks may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles, as well as other variations thereof, means thata particular feature, structure, characteristic, and so forth describedin connection with the embodiment is included in at least one embodimentof the present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This may be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

Referring now to FIG. 8, an alternative front end 802 is shown that hastwo separate transmission paths 106. This embodiment is similar to thatset forth in FIG. 2, but differs in that both paths include atransmission path for the respective polarization. Because each path nowhas a dedicated polarization, the splitter 214 is not included.Referring now to FIG. 9, a generic form of a switch 208 is shown. Atransistor 314 governs whether the switch 208 operates in a transmissionmode or a reception mode. In transmission mode, the switch 314 is openand a transmission input from amplifier 214 travels past a transmissionline 502 that has low impedance at the transmission frequency to theantenna output at 322. A second transmission line 504 has a lengthselected to minimize noise. In reception mode, the switch 314 is closed.The transmission line 306 has a high impedance at the receptionfrequency, such that received signals pass to a reception amplifier 204.

Having described preferred embodiments of a scalable polarimetric phasedarray transceiver and method of using the same (which are intended to beillustrative and not limiting), it is noted that modifications andvariations can be made by persons skilled in the art in light of theabove teachings. It is therefore to be understood that changes may bemade in the particular embodiments disclosed which are within the scopeof the invention as outlined by the appended claims. Having thusdescribed aspects of the invention, with the details and particularityrequired by the patent laws, what is claimed and desired protected byLetters Patent is set forth in the appended claims.

What is claimed is:
 1. A polarimetric transceiver front-end comprising:two receive paths configured to receive signals from an antenna, eachreceive path corresponding to a respective polarization, each comprisinga variable amplifier and a variable phase shifter; a first transmit pathconfigured to send signals to the antenna, said transmit path beingconnected to the variable phase shifter of one of said two receive pathsand comprising a variable amplifier; and a transmit/receive switchconfigured to select between the first transmit path and the two receivepaths for signals, the transmit/receive switch comprising aquarter-wavelength transmission line that adds a high impedance to thetransmit path when the transmit/receive switch is in a receiving state.2. The polarimetric transceiver front-end of claim 1, further comprisinga transmission polarization switch configured to select a polarizationfor transmission.
 3. The polarimetric transceiver front-end of claim 2,wherein the transmission polarization switching mechanism connects tothe transmit/receive switch.
 4. The polarimetric transceiver front-endof claim 1, further comprising a digital control configured to providesettings to the variable phase shifters, the variable amplifiers, andthe transmit/receive switch.
 5. The polarimetric transceiver front-endof claim 1, further comprising a second transmit path configured to sendsignals to the antenna, said transmit path being connected to thevariable phase shifter of the receive path not connected to the firsttransmission path, said transmit path comprising a variable amplifier.6. The polarimetric transceiver front-end of claim 5, wherein the firstand second transmit paths correspond to respective orthogonaltransmission polarizations.
 7. A polarimetric phased array transceiver,comprising: a plurality of front-ends configured to transmit and receivesignals, each front end comprising: two receive paths configured toreceive signals from an antenna, each receive path corresponding to arespective polarization, each comprising a variable amplifier and avariable phase shifter; a first transmit path configured to send signalsto the antenna, said transmit path being connected to the variable phaseshifter of one of said two receive paths and comprising a variableamplifier; and a transmit/receive switch configured to select betweenthe first transmit path and the two receive paths for signals, thetransmit/receive switch comprising a quarter-wavelength transmissionline that adds a high impedance to the transmit path when thetransmit/receive switch is in a receiving state; a first power combinerconfigured to combine the received signals from a first receive path ofeach of the plurality of front ends; and a second power combinerconfigured to combine the received signals from a second receive path ofeach of the plurality of front ends and further configured to split atransmission signal to the transmit path of each of the plurality offront ends.
 8. The polarimetric phased array transceiver of claim 7,further comprising a plurality of dual polarization antennas, eachantenna associated with a respective front-end.
 9. The polarimetricphased array transceiver of claim 7, further comprising a transmissionpolarization switch configured to select a polarization fortransmission.
 10. The polarimetric phased array transceiver of claim 9,wherein the transmission polarization switching mechanism connects tothe transmit/receive switch.
 11. The polarimetric phased arraytransceiver of claim 7, further comprising a digital control configuredto provide settings to the variable phase shifters, the variableamplifiers, and the transmit/receive switch.
 12. The polarimetric phasedarray transceiver of claim 11, wherein the digital control comprises abeam configuration register that stores values for each of said settingsthat correspond to predetermined beam directions.
 13. The polarimetricphased array transceiver of claim 7, wherein each front end furthercomprises a second transmit path configured to send signals to therespective antenna, said transmit path being connected to the variablephase shifter of the receive path not connected to the firsttransmission path, said transmit path comprising a variable amplifier.14. The polarimetric phased array transceiver of claim 13, wherein thefirst and second transmit paths correspond to respective orthogonaltransmission polarizations.
 15. The polarimetric phased arraytransceiver of claim 7, further comprising a signal distribution networkconfigured to accept a local oscillator signal input and to retransmitthe local oscillator signal to one or more other polarimetric phasedarray transceivers.
 16. The polarimetric phased array transceiver ofclaim 7, further comprising a signal distribution network configured toaccept combined signals from the power combiners and to combine saidcombined signals with respective signals from one or more otherpolarimetric phased array transceivers.
 17. A polarimetric phased arraytransceiver, comprising: a plurality of front-ends configured totransmit and receive signals associated with a respectivedual-polarization antenna, each front end comprising: two receive pathsconfigured to receive polarized signals from the antenna, each receivepath corresponding to a respective polarization, each comprising avariable amplifier and a variable phase shifter; a first transmit pathconfigured to send signals to the antenna, said transmit path beingconnected to the variable phase shifter of one of said two receive pathsand comprising a variable amplifier; and a transmit/receive switchconfigured to select between the first transmit path and the two receivepaths for signals, the transmit/receive switch comprising aquarter-wavelength transmission line that adds a high impedance to thetransmit path when the transmit/receive switch is in a receiving state;a first power combiner configured to combine the received signals from afirst receive path of each of the plurality of front ends; a secondpower combiner configured to combine the received signals from a secondreceive path of each of the plurality of front ends and furtherconfigured to split a transmission signal to the transmit path of eachof the plurality of front ends; and a signal distribution networkconfigured to accept a local oscillator signal input and to retransmitthe local oscillator signal to one or more other polarimetric phasedarray transceivers and further configured to accept combined signalsfrom the power combiners and to combine said combined signals withrespective signals from one or more other polarimetric phased arraytransceivers.
 18. The polarimetric phased array transceiver of claim 17,further comprising a transmission polarization switch configured toselect a polarization for transmission.
 19. The polarimetric phasedarray transceiver of claim 18, wherein the transmission polarizationswitching mechanism connects to the transmit/receive switch.
 20. Thepolarimetric phased array transceiver of claim 17, further comprising adigital control configured to provide settings to the variable phaseshifters, the variable amplifiers, and the transmit/receive switch.